1. Field of the Invention
The invention relates to the field of microelectronic calculator/controllers and more particularly to a single chip calculator/controller having a parallel storage arrangement.
2. Prior Art
Single chip calculator/controllers and microcomputers are well-known in the art. Such devices can range from relatively simple calculator chips with fixed storage and microroutines up to very powerful and flexible microcomputers capable of handling data processing functions or for use as a resident controller in a larger computer system.
The logic organization or architecture chosen for a particular device dictates the size and complexity of fabrication of the resultant chip and the flexibility of its microprogrammed instructions. The more powerful and flexible the logic functions desired, the greater the complexity of the resulting chip. However, with increasing complexity comes increased cost in fabrication and in testing. Oftentimes an entire chip must be discarded because of a single flaw in its fabrication.
Prior art calculator/controller systems generally have included a program storage unit (usually a read only memory) which contains an assembly of instructions, active storage elements (shift registers or a random access memory) the contents of which can be modified by the instructions contained in the program storage unit, and a processing unit which sequences the instructions and modifies the data contents of the active storage elements as specified by the instructions. In prior art devices the active storage elements are dedicated to specific functions and require specific hardware, control signals, and associated interconnections for their operation. For example, an index register (a pointer) is generally associated with an increment/decrement circuit and control signals, and an input/output register is normally hardwired to perform shift operations. Such structures in prior art devices do not take full advantage of the existing hardwired logic as only a limited subset of the instruction repertoire can act upon the data contents of any given active storage element. In general, prior art devices have required separate interconnections between each active storage unit and its associated logic unit thus greatly increasing the complexity of the circuitry.